[postgis-devel] Does ST_Max_Distance work on anyone's install

[Obe, Regina]

Ah okay I agree with Strk on that one. 

 For the example he gave I would expect
it to return 10 too since I think the common use case would be for example

Given a road a and road b -- what's the furthest that anyone would need to trek
(excluding routing obstacles)  from anywhere on road a to get to anywhere on road b.

Hmm I wonder how much effort it would be to fix it.  I guess strk gave up on it
so that would mean I am probably  too stupid to attempt it.  Pity though.

Well as functions go I guess its not the most important thing.  Would be more useful for polygons anyway since city to city commuting is more interesting.

-----Original Message-----
From: postgis-devel-bounces at postgis.refractions.net on behalf of Paul Ramsey
Sent: Wed 10/29/2008 12:23 PM
To: PostGIS Development Discussion
Subject: Re: [postgis-devel] Does ST_Max_Distance work on anyone's install
 
And there's the answer:

http://postgis.refractions.net/pipermail/postgis-devel/2004-August/000437.html

On Wed, Oct 29, 2008 at 9:21 AM, Paul Ramsey <pramsey at cleverelephant.ca> wrote:
> I'm pretty sure it existed and worked at one point, because Dave wrote
> it originally for a particular data processing use case Refractions
> had. Why strk turned it off is for him to say :)
>
> P.
>
> On Wed, Oct 29, 2008 at 4:17 AM, Mark Cave-Ayland
> <mark.cave-ayland at siriusit.co.uk> wrote:
>> Obe, Regina wrote:
>>>
>>> http://postgis.refractions.net/documentation/manual-svn/ST_Max_Distance.
>>> html
>>>
>>> I noticed Robert Burgholzer tried to use it and couldn't either
>>> evidentally.  Though I thought it worked once upon a time.
>>
>> Strange. There is actually code in the function to "do things"TM but the
>> elog() at the top of the function causes it to exit straightaway!
>>
>> Looking at svn log you can see the following comments:
>>
>> ------------------------------------------------------------------------
>> r756 | strk | 2004-08-26 17:55:09 +0100 (Thu, 26 Aug 2004) | 2 lines
>>
>> max_distance() raises an 'unimplemented yet' error.
>>
>> ------------------------------------------------------------------------
>>
>> ...
>>
>> ------------------------------------------------------------------------
>> r753 | strk | 2004-08-26 16:02:59 +0100 (Thu, 26 Aug 2004) | 2 lines
>>
>> Added (bogus) max_distance(geom,geom)
>>
>> ------------------------------------------------------------------------
>>
>>
>> And the relevant commit diff is:
>>
>> pg83 at zeno:~/src/postgis-svn/trunk/lwgeom$ svn diff -r 755:756
>> lwgeom_functions_basic.c
>> Index: lwgeom_functions_basic.c
>> ===================================================================
>> --- lwgeom_functions_basic.c    (revision 755)
>> +++ lwgeom_functions_basic.c    (revision 756)
>> @@ -1735,6 +1735,9 @@
>>        double maxdist = 0;
>>        int i;
>>
>> +       elog(ERROR, "This function is unimplemented yet");
>> +       PG_RETURN_NULL();
>> +
>>        geom1 = (LWGEOM *)PG_DETOAST_DATUM(PG_GETARG_DATUM(0));
>>        line1 = lwline_deserialize(SERIALIZED_FORM(geom1));
>>        if ( line1 == NULL ) PG_RETURN_NULL(); // not a linestring
>>
>>
>> I'd say from this that strk had a go at implementing this function but
>> realised it didn't work properly and so disabled it soon afterwards :(
>>
>>
>> HTH,
>>
>> Mark.
>>
>> --
>> Mark Cave-Ayland
>> Sirius Corporation - The Open Source Experts
>> http://www.siriusit.co.uk
>> T: +44 870 608 0063
>> _______________________________________________
>> postgis-devel mailing list
>> postgis-devel at postgis.refractions.net
>> http://postgis.refractions.net/mailman/listinfo/postgis-devel
>>
>
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